Ballistic Branched Flow of Almost Everything
Branched flow results from a common situation involving wave or ray propagation through weakly deflecting random media for long path lengths. In nature it affects light waves, radio and microwaves, sound waves, ocean waves and matter waves in important ways. Yet its importance is just beginning to be recognized in some of the fields it affects. For example imaging by scanning probe microscopy by the Westervelt group at Harvard recently revealed branched electron flow in 2DEG semiconductor microstructures with vanishing or modest magnetic fields.
Branched flow is often the form taken by momentum diffusion and it determines the coherent mean free path. Branched flow effects have successfully explained observed large enhancements of freak wave probability in the world's oceans. This in turn has been modeled with microwaves in the laboratory of Prof. Dr. Hans-Jurgen Stockmann in Marburg. Recent theoretical progress and experiments point to branched flow as a growing field with many applications. Interesting theoretical questions involving formation of the branches, control of branched flow, wave-ray correspondence, source averaging, and more remain and will be described in this talk, along with the nature and applications of branched flow mentioned above.